Although nervous systems contain staggering numbers of neurons, it is possible to use electrophysiological, morphological, and molecular markers to classify neurons. Classification can become specific enough, especially in invertebrates, to identify individual neurons and map distinct neural circuits. Classifying neurons and mapping circuits is extremely valuable for neuroscience, as it elucidates the fundamental structure of the nervous system, providing a framework for understanding brain dysfunction. Unfortunately, progress is slow, as the work is tedious and there is no standard way to represent, store, and analyze the neuron types and wiring diagrams that emerge from these efforts. To help improve progress this project will develop NeuronBank, a public, on-line database of identified neurons and their synaptic connections that will serve as an important knowledge source and a novel informatics tool for the identification of new neuron types. Through collaboration between neuroscientists and computer scientists, a prototype NeuronBank will be developed that supports rich, flexible descriptions of identified neurons, allows features important to identification to be flagged, and provides source information and citable accession numbers. To facilitate further circuit mapping, NeuronBank will have facilities for comparing new observations to known cell types and suggesting diagnostics for determining if the cell is novel. NeuronBank will also feature an innovative 3-D visualization system to intuitively represent neuron location. The implementation will allow additional NeuronBank databases to be installed and modified easily by other researchers, enabling the evolution of a federation of databases uniting broad data sets. To road- test the prototype, NeuronBank will be stocked with large data sets from the molluscs Tritonia diomedea and Aplysia californica, both important model systems for motor pattern generation, learning, and memory. NeuronBank will then be used as an informatics tool to explore these systems for new neuron types. This proposal serves the purposes of PAR-03-036 (Innovative exploratory studies and technology development in Neuroinformatics Research) in several ways. It develops a new database and tools for neuroinformatics research. It is likely to have a high impact on future neuroscience research as it implements a unique neuroinformatics approach to neuron identification and neural circuit analysis. [unreadable] [unreadable]